The present invention relates to an ultrasonic multitransducer probe with transducers of different sizes and is more particularly used in the non-destructive testing of mechanical parts.
Numerous ultrasonic multitransducer probes are known. They are all formed from geometrically identical transducers of the same size. In exemplified manner, FIG. 1 diagrammatically shows a known probe. For example, it is intended for use in the inspection or testing of a weld 2 by means of which two parts 3a and 3b are joined to one another, so as to form a single part 3. The probe shown in FIG. 1 comprises a linear strip 4 of M juxtaposed transmitter-receiver ultrasonic transducers 5, which are directed towards the part 3 to be inspected. The strip 4 is inclined relative to the surface 6 of part 3, the weld 2 being perpendicular thereto. Strip 4 is electrically connected to means 7 for activating a group 9 of m juxtaposed transducers of strips 4, so as to make them function firstly as ultrasonic transmitters and then as ultrasonic receivers. The said group of activated transducers is then displaced by an integral number of transducers, said number being e.g. equal to 1, so as to scan the complete strip 4 and thus investigate the part 3 in depthwise manner and consequently weld 2 over its entire height. The means 7 making it possible to displace the group of activated transducers is electrically connected to means 8 for the volume display of part 3.
Transducers 5 are all of the same size, i.e. have the same receiving-transmitting zone width (considered in the lengthwise direction of the strip). The group of m transducers is equivalent to a single transducer, whose size is equal to m times the size of the transducers forming the group. The activation of the transducers 5 of strip 4 takes place starting from the transducers furthest from the surface 6 of part 3 and proceeding to the transducer closest to its surface.
FIG. 1 shows that the width d of acoustic beam 10 transmitted by the group 9 of m transducers increases with the weld depth p. As the group 9 of m transducers is displaced by a constant step following each activation, the redundancy rate, corresponding to the number of times a point defect 11 (of the weld 2 in the present case) is impinged upon by the acoustic beam 10, increases with the depth p. Therefore the probe of FIG. 1 suffers from the disadvantage that it is only possible to inspect part 3 at a reduced speed.
It is possible to conceive other multitransducer probes making it possible to retain a constant redundancy rate, i.e. independent of the depth, so as to obtain a higher inspection speed by simultaneously increasing, when the depth p increases, the number m included in the elements of group 9 of activated transducers and the advance or displacement step of said group. These other multitransducer probes therefore suffer from the disadvantage of requiring very complex electronic control means.